Episode 35 starts by checking in on the mystery in Connie’s village, which was devastated but where there are no human remains, and where every horse is still in the stables. So what the hell happened? We don’t learn the answer to that, only that the sole Titan in the village—the one that looks like it’s fallen and can’t get up—is indeed Connie’s mother.
Moving on, we return to Reiner, Bertholdt. With scouts approaching, they have no choice but to get moving before nightfall. Eren pretends to cooperate—for all of five seconds—only to struggle in vain; he’s still too messed up to transform.
Reiner takes Eren and Bertholdt takes Ymir, who is still not sure who to trust. Reiner likes Christa too, and she factors into their “plans” (whatever they are), so Ymir goes along, until she senses Christa is among the pursuing scouts, and decides she’s going to do things her way.
That decision comes after a lifetime far longer than the age Ymir appears, in which lies she told herself and others temporarily placed her in places of comfort and purpose, only for everything to turn to shit.
In the earliest instance, cultists pick her up off the street and make her their icon, claiming she has the blood of the king. When troops raid the cult, she lies about deceiving them to save lives, only for all of them to share the same fate.
That fate involves some kind of sentencing that involves turning the condemned into a Titan and shoving them off the wall. On the other side, Titan Ymir wandered, suffered, and ultimately fell dormant and became buried by the earth.
When she finally wakes up, instinct leads her to eat Reiner and Bertholdt’s comrade Marcel…but doesn’t remember doing so. When she returns to human form, she’s greeted by a gorgeous starry sky, and makes it her new purpose in life to stop dealing in lies and live the way she wants, leading her to Christa, whom she considers a kindred spirit.
It’s a bold, engrossing tale that further fleshes out Ymir the person, made more intriguing by all the questions and lines of thinking that it raises during the flashback—questions a non-source-reader like me has no knowledge of—questions about the nature of humans and Titans; whether everyone has a Titan within them; even whether the state of human civilization within the walls is the true aberration in this strange world.
Back in the present, rather than simply going along with whatever plan (or lack thereof) Reiner and Bert have, Ymir flips the script. She wrenches herself loose from Bertholdt and demands they let her bring Christa with them, or else she’ll take Eren and escape on her own using her superior speed and agility.
The lads seem to agree, because when Mikasa, Armin & Co. arrive at Ymir’s position, she’s become a Titan, and when Christa arrives, she swallows her whole (for ease of transport, not to eat her) and rejoins Reiner (in Armored Titan form), Bert and Eren, running off into the sunset, having thoroughly outwitted the scouts.
Of course, the scouts aren’t done chasing them. Erwin, as well as Mikasa and Armin, have come this far; they’re not returning home without Eren or Christa. And so the pursuit continues.